that there were no known recorded defects on the involved aircraft in the last 15 days. Pakistani CAA also claimed that the Fokker F27 fleet was airworthy. Engine malfunction Investigators visited the crash site on the same day of the crash. Following report from air traffic control that the aircraft had caught fire during the take-off, the runway was inspected for possible clues. The team discovered a metal debris lying on the right side of the runway at a distance of 4,000 ft down the runway. The grass surrounding the area had signs of fire. While continuing through the entire length of the runway, they discovered that more pieces of metal debris had spread until at a distance of 6,800 ft. The identification of the metal debris revealed that the pieces were actually parts of the aircraft's turbine blades, specifically from the right engine. A teardown on the right engine further revealed that the two bolts which retained the bearing of the rear turbine had cracked due to stress. A third bolt had also fractured in the same way. The stress had originated from the inner part of the ball bearing, which eventually led to metal fatigue. The inner portion had been too extensively damaged that investigators could not determine the primary source of the failure, but it was thought that the failure had occurred prior to the flight on 10 July. Further examination showed that the clamping load on the bearing assembly had lost. Subsequently, the bearing assembly moved from its place and the turbine followed the movement of the ball bearing. This resulted in a physical contact (rub) between the rear part of the high pressure turbine (HPT) blades and intermediate pressure turbine (IPT). Due to the rub, the root neck part of the blades overheated and the blades eventually broke off in high temperature. The IPT turbines also contacted the low pressure turbine (LPT), causing fatigue as well. The resulting separation of the blades caused deterioration in the engine performance. These blades were also noted as the ones that caused the fuel to ignite during the crash. The bolts which held the bearing in its place had cracked due to bending stress. The stress was caused by improper assembly, which happened during the last overhaul of the engine at a local PIA facility in September 2005. According to investigators, the thrust bearing had "some eccentricity" during the